linux-kernel - Re: [PATCH 2/4] kprobes/x86: use instruction_pointer and instruction_pointer

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Date:   Tue, 20 Aug 2019 09:09:35 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jisheng Zhang <Jisheng.Zhang@...aptics.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "David S. Miller" <davem@...emloft.net>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] kprobes/x86: use instruction_pointer and
 instruction_pointer_set

On Mon, 19 Aug 2019 11:36:48 +0000
Jisheng Zhang <Jisheng.Zhang@...aptics.com> wrote:

> This is to make the kprobe_ftrace_handler() common, so we can move it
> to common code in next patch.
> 

BTW, this patch looks good, without next patch. Could you update the
patch description and resend it with my Ack?

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you,

> Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
> ---
>  arch/x86/kernel/kprobes/ftrace.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
> index 681a4b36e9bb..c2ad0b9259ca 100644
> --- a/arch/x86/kernel/kprobes/ftrace.c
> +++ b/arch/x86/kernel/kprobes/ftrace.c
> @@ -28,9 +28,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  	if (kprobe_running()) {
>  		kprobes_inc_nmissed_count(p);
>  	} else {
> -		unsigned long orig_ip = regs->ip;
> +		unsigned long orig_ip = instruction_pointer(regs);
>  		/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */
> -		regs->ip = ip + sizeof(kprobe_opcode_t);
> +		instruction_pointer_set(regs, ip + sizeof(kprobe_opcode_t));
>  
>  		__this_cpu_write(current_kprobe, p);
>  		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> @@ -39,12 +39,13 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  			 * Emulate singlestep (and also recover regs->ip)
>  			 * as if there is a 5byte nop
>  			 */
> -			regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
> +			instruction_pointer_set(regs,
> +				(unsigned long)p->addr + MCOUNT_INSN_SIZE);
>  			if (unlikely(p->post_handler)) {
>  				kcb->kprobe_status = KPROBE_HIT_SSDONE;
>  				p->post_handler(p, regs, 0);
>  			}
> -			regs->ip = orig_ip;
> +			instruction_pointer_set(regs, orig_ip);
>  		}
>  		/*
>  		 * If pre_handler returns !0, it changes regs->ip. We have to
> -- 
> 2.23.0.rc1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>